Partial view of the Earth centred on the Pacific Ocean with Moon in background.
Image: NASA, JPL
Source: NASA, JPL
Earth and the other planets formed from a cloud of gas and dust 4.5 billion years ago. It is thought that the Moon formed soon after when a massive object collided with Earth and threw a chunk of Earth into space.
After cooling and solidifying, Earth was soon awash with oceans of water produced by chemical reactions in its young crust, and from impacts of icy comets. Earth’s rotation and the gravitational pull of the Moon created tides in these oceans.